NEW YORK (BLOOMBERG) - Covid-19 vaccine side effects that range from fevers and chills to headaches and joint pain could keep some doctors and nurses from working amid a nationwide surge in hospitalisations.

Health systems are gearing up to vaccinate key hospital staff with the Pfizer Inc and Moderna Inc coronavirus shots, which could start shipping in the United States in a matter of weeks, pending emergency use authorisations.

Earlier this week, federal advisers recommended US healthcare workers be immunised first, along with residents of long-term care facilities.

For hospitals, that could pose significant scheduling issues at a time when many are filling up. More than 100,000 Americans were hospitalised with the virus on Wednesday (Dec 2), according to data from the Covid Tracking Project.

Providers will need to pull medical staff from the bedside to the vaccination clinic to get their shots. And if side effects do occur, they could lose key workers for a couple of days.

To overcome this, some hospitals plan to stagger staff to keep units covered. Others are exploring giving workers the shots at the end of their shifts, before they have a few days off.

Still, it's difficult to know what to expect without seeing full data from Pfizer and Moderna's large, late-stage clinical trials, said Dr Paul Biddinger, vice-chair of emergency preparedness at Massachusetts General Hospital.

"It's a little easier to create a model for how we should stagger employee vaccinations when we know how commonly (side effects) are occurring and with what severity," Dr Biddinger said. Plans could change when more robust data becomes available, he added.

Though the pharmaceutical companies have yet to release full results from their largest trials, disclosures from earlier tests in recent press releases give a sense of their safety profiles.

Pfizer and its German partner BioNTech SE said on Nov 18 that no serious safety concerns were observed in their late-stage trial. Among participants who got the two-dose vaccine regimen, 3.8 per cent experienced fatigue, and 2 per cent had headaches. Older adults reported fewer and milder adverse events. In an earlier trial, the companies identified cases of mild-to-moderate fever.

Moderna, meanwhile, said on Nov 16 that it had also identified no serious safety concerns in its late-stage trial. Mild-to-moderate side effects included fatigue (9.7 per cent), muscle or joint pain (5.2 per cent), headache (4.5 per cent) and injection-site pain (2.7 per cent). The side effects were more common after the second dose of the two-dose vaccine.

"We have been very reassured that we have not seen cases of things we would not expect," said Dr Buddy Creech, the director of Vanderbilt Vaccine Research Programme who is leading trials of Covid-19 vaccines. "We see side effect profiles that are common to other vaccines we use."

Small proportion

Only a small proportion of those who get coronavirus vaccines will confront side effects, according to Dr Creech, who also serves as the principal investigator for both Moderna and Johnson & Johnson's Phase 3 clinical trials.

Remember, "it's not 100 per cent of people who have fevers and chills", Dr Creech said Thursday during a media panel held by the Infectious Disease Society of America, of which he is a member.

However, the potential that there might be side effects strong enough to put health workers out of commission needs to be raised before the vaccination campaign begins, Dr Creech said.

If the possibility isn't effectively communicated, he added, hospitals might be left understaffed. At the same time, medical workers must also be taught to distinguish between side effects from the vaccine and symptoms from Covid-19, given they are highly exposed to the virus.

"We will need to be somewhat strategic about who is offered the vaccine, so we're working with clinical leads in those areas to make sure they stagger out their healthcare personnel," said Dr Jeanmarie Mayer, chief of infection prevention at University of Utah Health, said Thursday at a press conference.

Utah-based Intermountain Healthcare is one system that may vaccinate workers at the end of their shifts before they have a few days off, said Dr Kristin Dascomb, the medical director of infection prevention and employee health.

"When you're having your weekend off, you might have the opportunity to have the symptoms, as mild as they might be, so that you're not taking time off away from work when we are stressing caregivers at this time," Dr Dascomb said at the news conference.

Hospitals are generally planning to prioritise staff who work directly with coronavirus patients since they are at the greatest risk of contracting the disease on the job.

Mass General's Dr Biddinger worries healthcare workers who confront unexpected symptoms might panic and think the shots are faulty, sowing even more mistrust among an already skeptical public.

"We're trying to be very honest about what people should expect when they get the vaccine, but to remind them that it's a good thing and it actually means that vaccination is helping us get more immune," he said.